Lattice girder



March 31, v1959 E. SCHMIDT 2,879,661

LATTICE GIRDER Filed Dec. 21, 1955- 2 Sheets-Sheet 1' FIG! G 2 FIG.4

INVENTOR. [QM/v- Jwzv/p 7- March 31,1959 E. SCHMIDT 2,879,661

LATTICE GIRDER Filed Dec. 21, 1953 2 Sheets-Sheet 2 United States Patent LATTICE GIRDER Ernst Schmidt, Main-Bischofsheim, Germany, assignor to Rhembau G.m.b.H., Main, Germany, a firm Application December 21, 1953, Serial No. 399,378 Claims priority, application Germany December 22, 1952 6 Claims. (Cl. 72-61) This invention relates to a girder suitable for use in masonry or concrete structures.

'One object of the invention is to provide a girder which will be especially useful in the construction of reinforced concrete ceilings and which will combine great structural strength with lightness in weight and comparatively low cost.

According to the invention, the girder is expanded from a strip of comparatively light but strong material, such as sheet metal, to form an upper and two lower chords or booms connected to each other by two rows of oppositely inclined diagonal ties or struts. The ties of each row are inclined in the same direction and slope inwardly from the lower toward the upper chord, with the ties in one row being longitudinally staggered in relation to the ties in the other row. Cross connecting clips are mounted between and engage the lower chords. The clips are in a tensioned state and hold the chords against lateral and longitudinal movement.

Girders made in accordance with this invention do not require any riveting or welding in the course of their production. They are light in weight and yet can support very great loads. Another advantage resides in the ease of transportation of the girder. The incised strips can be transported in fiat condition to their places of use and may be expanded there to the lattice shapes which they are to have in their ultimate state.

Girders according to the invention are particularly useful in floor or ceiling construction. The lower chords are embedded in a concrete slab, with adjacent reinforced slabs supporting blocks between them to form a coherent ceiling together with the blocks. They can also be used as supports, purlins, sills, and for many similar purposes.

Expanded lattice sheet metal reinforcements have previously been used. Their upper and lower chords were also connected by diagonal members formed by expansion of a strip of sheet metal. ferent arrangement of the incisions in the sheet metal, conventional expanded structural elements were not load supporting but were usable for the arming of concrete only. Particularly at the roots of the diagonal ties the cross sections were so weak and the stresses under load became so great that the employment of these lattice structures as load-supporting girders was not possible.

The accompanying drawings illustrate several embodiments of the invention by way of example. In these drawings:

Fig. 1 is a plan view of a strip of sheet metal which has been provided with a number of incisions in accordance with the invention.

Fig. 2 is a cross section through the strip shown in Fig. 1 taken on line IIII of that figure.

Fig. 3 illustrates the structure shown in Fig. 2 and strengthened by the formation of'beads and ribs in the sheet material.

Fig. 4 represents a partial view of a girder in accord- However, because of the difmice with the invention with parts lbeing'shown in section. 4

Fig. 5 shows part of the expanded girder in perspective. Fig. 6 is a perspective view of a cross connecting clip. Fig. 7 is a modified form of such a clip.

Fig. 8 illustrates a vertical cross section through a girder constructed in accordance with the invention.

Fig. 9 diagrammatically indicates the application of a girder according to the invention as a roof purlin.

Fig. 10 shows the employment of a girder according to the invention as a lower ceiling beam.

In the drawings 1 denotes a strip of sheet material, preferably sheet metal, into which pairs of incisions 2 and 3 have been cut at an inclination to the longitudinal axis of the strip. Suitable cutting dies may be used for this purpose. Two rows of incisions are arranged adjacent to each other, the rows being positioned symmetrically on each side of the longitudinal axis of the strip. When the sheet metal strip is expanded, the areas 4 between each two incisions 2 and 3 form the connecting ties between the upper and lower chords of the girder. Beads 5 are preferably provided at the ends of these areas 4 at right angles to the incisions, which beads are directed alternately up and down; the upwardly directed beads being designated 5a and the downwardly directed ones 5b. The purpose of these heads is to apply a slight stretch to the small strips left between the incisions, which has been found to impart additional resilient strength to the joints of the ties at the upper and lower chords.

As will be seen from Figs. 2 and 3, the areas between the incisions 2 and 3 are slightly bulged so as to form a channeled cross section for the purpose of greater strength. It is preferable to apply the bending force to the areas 4 simultaneously with the cutting of the incisions. Also at the same time or immediately afterwards, the shaping of the reinforcing ribs 6 and 7 and the'formation of" rims 8 may be carried out.

After the strips have been prepared in the aforesaid manner, they are pulled out in their longitudinal direction, whereby an upper chord or boom 9 is formed in the center and two lower chords 10 at the sides, which are connected to one another by the ties or struts 11. The beads 5 act as pivots during the formationpf the ties 11 and prevent undue straining of the material at these places.

Due to the oblique disposition of the incisions, the portion of the chords where each tie is integrally joined with and merges into the chords is comparatively large, as can be seen from Fig. 5, so that comparatively large loads can be supported by the girder. Besides, the peculiar location of the incisions forces the ties 11 to slope outwardly from the central chord 9 to the two coplanar chords 10 when the strip is expanded into the girder. The girder is brought into its ultimate shape by pressing the lower chords together with clips 13 so that the ties are in an approximately vertical plane as shown in Fig. 8. The lower chords may be embedded in a slab 12 of concrete which, at the same time, serves as a rust preventive. The lower chords are held against lateral and longitudinal movement by cross connecting clips 13, which impart to the girder a pre-tension in at least its direction of width. This pre-tension enables the girder prior to its being embedded in the concrete to be subjected to comparatively high loads, without distortions in any direction.

As shown in Fig. 6, the clip may consist of a plate 13 having bent-over flanges 14 so as to be able to grip the lower chords 10 as illustrated in Fig. 8. At the places at which the clip abuts the ties 11, which is at the place of the aforesaid beads 5, ridges 15 may be bent out of the plane of the clip to provide an increased contact area between the clips and the ties 11.

As shown in Figs. 6 and 7, the clips 13 may, at the same time, serve to hold longitudinal strengthening members,-such as roof spars, bars and thelike (not shown),

3 t for which purpose appropriate fixing members, such as prongs 16 or tabs 17 may be provided.

Fig. Qdiagrammatically shows the girder 18 used as a root purlin to support a plate 19 attached to the lower booms by bolt 20 passing through the clips 13. In the case of Fig. 10, the lower chords of the girder 18 are embedded in a slab 21 of concrete (as shown in Fig. 8) upon which the ceiling panels are supported held in position by the, tabs 17 (see Fig. 7).

The invention is not intended to be limited to the embodiments shown and described. It includes all girder constructions of expanded sheet material in which inclined parallel incisions are made in the sheet material to obtain diagonal connecting ties upon expansion of the sheet and which has cross ties in a tensioned state, to prevent the Iclative movement of the individual parts of the girder.

What I claim is;

l, A lattice girder comprising an integral expanded sheet n etal tripc nsisting of a. p i f. pa l l, plan chords, a third chord in a plane parallel to and spaced 1108 he plane of the pair of chords, the third chord being positioned centrally of said pair of chords, and two rows of oppositely inclined connecting ties, the ties of each row being inclined in the same direction and connecting a respective one of said coplanar chords with the third chord and sloping inwardly from the coplanar chords toward the centrally positioned third chord, the ties in one row being longitudinally staggered in relation to the ties in the other row to, form successive pairs of laterally adjacent but spaced apart ties which cross each other, each tie being integrally joined to said third chord by a joining portion of said third chord, which is equal in width to the width of the tie, the joining portion, between longitudinally adjacent ties, tapering in width from the tie width to substantially zero width at the point of jointure of an adjacent tie; and cross connecting clips mounted between and engaging the coplanar chords, said clips being in a tensioned state and holding the coplanar chords against lateral and longitudinal movement.

2. A lattice girder comprising an integral expanded sheet metal strip consisting of a pair of parallel, coplanar chords, a third chord in a plane parallel to and spaced from the plane of the pair of chords, the third chord being positioned centrally of said pair of chords and two rows of oppositely inclined connecting ties, which are channelshaped in cross section, the ties of each row being inclined in the same direction and connecting a respective one of said coplanar chords with the third chord and sloping in- Wardly from the coplanar chords toward the centrally positioned third chord, the ties in one row being longitudinally staggered in relation to the ties in the other row to form successive pairs of laterally adjacent but spaced apart ties which cross each other, each tie being integrally joined to said third chord by a joining portion of said third chord, which is equal in width to the'width of the tie, the joining portion, between longitudinally adjacent ties, tapering in width from the tie width to substantially zero width at the point of jointure of an adjacent tie; and cross connecting clips mounted between and engaging the coplanar chords, said clips being in a tensioned state and holding the coplanar chords against lateral and longitudinal movement.

3. A lattice girder comprising an integral expanded sheet metal strip consisting of a pair of parallel, coplanar chords, a third chord in a plane parallel to and spaced from the plane of the pair of chords, the third chord being positioned centrally of said pair of chords, and two rows of oppositely inclined connecting ties, the tiesof each row; being; inclined in thesame direction and connecting arespective onev of said coplanar chords with the third chordand slopinginwardly fromthe coplanar chords to ward the centrally positioned third chord, the ties in one rowbeingrlongitudinally staggered, in relation to he ties inthe other row. to form successive pairs of laterally adjacent but spaced apart ties which. cross; ith .Qfll a 95 tie being integrally joined to said third chord by a joining portion of said third chord, which is equal in width to the width of the tie, the joining portion, between longitudinally adjacent ties, tapering in width from the tie width to substantially zero Width at the point of jointure of an adjacent tie; and cross connecting clips mounted between and engaging the coplanar chords, the clips being in a tensioned state and extending between said pairs of ties and each clip abutting one tie of one pair in the one row of ties and one tie of the successive pair in the other row of ties to hold the coplanar chords against lateral and longitudinal movement.

4. A lattice girder comprising an integral expanded sheet metal strip consisting of a pair of parallel, coplanar chords, a third chord in a plane parallel to and spaced from the plane of the pair of chords, the third chord being positioned centrally of said pair of chords, and two rows of oppositely inclined connecting ties, the ties of each row being inclined in the same direction and connecting a respective one of said coplanar chords with the third chord and sloping inwardly from the coplanar chords toward the centrally positioned third chord, the ties in one row being longitudinally staggered in relation to the ties in the other row to form successive pairs of laterally adjacent but spaced apart ties which cross each other, each tie being integrally joined to said third chord by a joining portion of said third chord, which is equal in width to the width of the tie, the joining portion, between longitudinally adjacent ties, tapering in width from the tie width to substantially zero width at the point of jointure of an adjacent tie; and cross connecting clips mounted between and engaging the coplanar chords, the clips being in a tensioned state and extending between said pairs of ties and each clip abutting one tie of one pair in the one row of ties and one tie of the successive pair in the other row of ties to hold the coplanar chords against lateral and longitudinal movement, portions of the connecting clips abutting the ties being deformed to provide an increased contact area between the ties and the clips.

5. A lattice girder comprising an integral expanded sheet metal strip consisting of a pair of parallel, coplanar chords, a third chord in a plane parallel to and spaced from the plane of the pair of chords, the third chord being positioned centrally of said pair of chords, and two rows of oppositely inclined connecting ties,the ties of each row being inclined in the same direction and connecting a respective one of said coplanar chords with the third chord and sloping inwardly from the coplanar chords toward the centrally positioned third chord, the tics in one row being longitudinally staggered in relation to the tics in the other row to form successive pairs of laterally adjacent but spaced apart ties which cross each other, each tie being integrally joined to said third chord-by a joining portion of said third chord, which is equal in width to the width of the tie, the joining portion, between longitudinally adjacent ties, tapering in width from the tie width to substantially zero width at the point of jointure of, an adjacent tie; cross connecting clips mounted between and engagingthe coplanar chords, said clips-being in a tensioned state and holding the coplanar chords against lateral and longitudinal movement, and retaining elements on said cross connecting clips for holding longitudinally extending girder reinforcing means.

6. A lattice girder comprising an integral expanded sheet metal strip consisting of a pair ofparallel, coplanar chords, a third chord in a plane parallel to and spaced from the plane of the pair of chords, the third chord being positioned centrally of said pair of chords, andtwo rows oi oppositely inclined connecting ties, the ties-ofjcach row being inclined in the same; direction and connecting a respective one of said coplanar chords; with the third chord and sloping inwardly from the coplanar chords toward the centrally positioned third chord, the ties in one row, being longitudinally staggered in relation to the ties in the other row t flcrmsu cessivepairs of laterally adjacent but spaced apart ties which cross each other, each tie being integrally joined to said third chord by a joining portion of said third chord, which is equal in width to the Width of the tie, the joining portion, between longitudinally adjacent ties, tapering in width from the tie width to substantially zero width at the point of jointure of an adjacent tie; cross connecting clips mounted between and engaging the coplanar chords, said clips being in a tensioned state and holding the coplanar chords against lateral and longitudinal movement, and a concrete slab, said coplanar chords and cross connecting clips being embedded in said slab.

References Cited in the file of this patent UNITED STATES PATENTS 799,653 Kahn Sept. 19, 1905 6 White Feb. 12, 1907 Rogers Nov. 12, 1907 Simpson Nov. 17, 1908 Golding Mar. 24, 1914 Rough Feb. 6, 1917 Gockel July 11, 1922 Watson Nov. 3, 1925 Willis Nov. 9, 1926 Hahn Aug. 3, 1937 Faber Aug. 1, 1939 FOREIGN PATENTS France Oct. 18, 1906 Germany Apr. 28, 1952 

